Yagi 7 el. for 70 cm. band "Ecological"
The aerial was developed to use it during radio attendance. (Car and
cycle race, marathons, etc.)
So it was privileged the reduced dimension and the heavy-duty.
Electrically it was optimized the tuning on a large spectrum of the
band.
The computer project was done using Yagimax 311 di G. Lew Gordon, K4VX
(radiation diagrams) and DL6WU Antenna design by Jerry Haigwood, KY4Z e
Bob Stein, W6NBI, in respect of calculation and tables by Gunter
Hock, DL6WU.
For the building it was recycled material from surplus TV antennas.
A Fracarro VHF for the elements and a Prestel UHF for the boom and the
lockers. That’s why is called “Ecological”.
The dimension are rendered on the drawing.
Yagi
7el. Ecological
The total length of the boom is 1m. The lock to the master is on the
back of the reflector. The section is 1 x 2 cm.
The cylindrical aluminium elements are inserted in plastics support.
Their diameter is 6mm.
The folded dipole was copied, in the shape, by the original Prestel.
Photo
of dipole
The top-central part of the dipole is in contact with the boom.
The distance from the two sides is 4.5cm.
The original balun was emptied. Inside I have connected the new 4:1
coaxial cable balun.
Balun drawing
The theoric gain related to the dipole is 10 dB.
Field test has confirmed the calculation. No mechanical trim were necessary.
Dimensions
R.O.S. is low up to 436 MHz. The gain was compared to another
similar commercial antenna (8 el.). Recordable differences weren’t found.
@_giancarlo_paparella_2002
This
article was published on Radio Rivista n.7-2002
